Process of making sulfuric acid.



No. 642,390. Patented Jan. 30, [900.

r. P. VAN DENBEBGH. PROCESS OF MAKING SULFURIC ACID.

(Application filed Apr. 11, 1898. Bqnawed June 15, 1899.) (No Model.)

( L 2 Q E O MZZJC'nndensen a v A FRANK P. VAN DENBERGH,

PATENT OFFICE.

OF BUFFALO, NEW YORK.

PROCESS OF MAKING SULFURIC ACID.

SPECIFICATION forming part of Letters Patent No. 642,390, dated January30, 1900.

Application filed April 11, 1896. Renewed June 15,1899. Serial No.720,709. (No specimens.) I

To all whom it may concern:

Be it known that I, FRANK P. VAN DEN- BERGH, a citizen of the UnitedStates, residing at Buffalo, New York, have invented certain new anduseful Improvements in the Art or Process of Making Sulfuric Acid; and Ido hereby declare the following to be a full,

' clear, and exact description of the same, such as will enable thoseskilled in the art towhich it appertains to employ the same.

More particularly, my invention relates to a new and improved art orprocess for the production of sulfuric acid from gypsum or nativesulfate of calcium or other materials containing sulfur or its salts bymeans of heat and electrolysis, both produced by an electric current,with or without the presence of additional oxidizing and hydrating agentor agents.

In order to distinguish my process from that hitherto employed,referencewill now be made to the common means of producing sulfuric acid. Infollowing the common methods sulfur, iron pyrites, or copper pyrites areburned in a furnace especially constructed for the purpose, and thevapors of sulfur dioxid which result are passed over a series of pots orthrough a chamber containing nitrate of soda or other material capableof yielding the oxids of nitrogen. These fumes are together dischargedfrom the furnace or series of furnaces into a lead-lined tower filledwith coke or vitrified brick or other acid-resisting mate rial, andafter being denitrated by sulfuric acid, which is sprayed from abovedownward, the fumes are discharged into very large chambers, whose wallsare made of sheet-lead. The lead surface of these chambers is usuallyvery great, aggregating in some instances a total area equal to severalacres. The acidvapors are conducted from one of these lead chambers toanother and are finally discharged into a Guy-Lussac tower, lead-linedand similar in construction to the tower first mentioned. The acid thusproduced is what is known commercially as chamber-acid and contains fromforty to sixty per cent. of water, and to remove this Water it isnecessary to concentrate the acid by evaporating it in glass or platinumvessels. The glass vessels are very liable to fracture, involving lossof apparatus and material and also injury to workmen and plant. Theplatinum stills or pans are expensive, and therefore greatly increasethe investment necessary fora sulfuricacid plant. Whether the acid madein this way is obtained from brimstone or pyrites it is impure, and thatfrom pyrites especially contains a large proportion of arsenic and otherdeleterious substances from which it is absolutely necessary for manypurposes to purify the acid. The purification involves further expenseand time.

My invention has for its object to utilize an abundant raw materialhaving at present but little value in the industrial arts, to lessen thetime and cost of producing sulfuric acid, and at the same time to avoidthe necessity of purifying the acid for many of the purposes for whichit is now necessary to purify it, especially all purification necessaryfor the elimination of arsenic.

In carrying out my invention instead of reacting upon the sulfurous andsulfuric oxids obtained by burning sulfur or sulfids with nirogen oxidsobtained by heating saltpeter, and thus by slow and expensive meansobtaining an impure sulfuric acid, I use gypsum or native sulfate ofcalcium or other suitable materials containing sulfur or its salts andany suitable flux-such as ordinary sand, gravel, quartz, clay, shale,cullet, or other suitable material containing silicaand these I reduceto a molten mass Within the furnace-chamber by the heat of the electriccurrent. This fusion of the materials is caused to take place in anatmosphere which contains an excess of oxygen, which is supplied by anysuitable means, such as hematite iron ore or other suitable solid, whichmay be mixed with the materials fed into the furnace, or by steam, air,oxygen, ozone, or other suitable oxygen-yielding gas which may beinjected into the furnace, so that the decompositions and reactionswhich take place in the molten bath and the gases which are given offtherefrom take place and are in the presence of an excessive supply offree oxygen, or oxygen which is in a nascent state. This bath or moltenmass is subject to intense heat and also to electrolysis, both due tothe electric current, the heat principally serving to reduce thematerials to a fluid condition and the electrolysis serving principallyto effect decomposition of the materials. The gypsum and fiux beingtogether introduced into the furnace, the first effect is to fuse thesilica (SiO of the flux. Subsequently the gypsum under the influence ofthe electric current is decomposed, and the sulfur oxids being liberatedin an atmosphere containing an excess of free oxygen sulfur trioxid isformed, the reactions taking place being indicated by the formulaSO,Oa+SiO =Si0 Ca (silicate of calcium, which passes off with theresiduum as a slag) and 80,. While sulfur dioxid (50,) may be producedas an intermediate product, it is almost immediately converted into thetrioxid, owing to the excess of free oxygen present. The sulfur trioxidthus formed is next hydrated to form sulfuric acid, (SO H and to causethis reaction I prefer to supply the necessary hydrogen and oxygen byintroducing steam into the furnace, so that it will com mingle with thegases passing from the furnace, including the sulfurtrioxid, and combinewith this latter, as indicated by the formula So +H O:SO I-I Inoperating according to my process the gypsum or other materialcontaining the sulfur and the flux material are first broken or crushedto such a condition as to permit and facilitate feeding them into anelectric furnace and also facilitate their fusion. The electric furnaceemployed may be of any desired type, provided it has a properly-closedchamber and a proper exit for the Vapors generated connected with acondensing apparatus. It is especially advantageous, however, to employa furnace affording a continuous process of red notion-that is,of fusionand decomposition.

In the drawing accompanying this case I have illustrated in centraltransverse section an electric furnace adapted to the carrying out of myinvention, all details of construction and arrangement being omitted inso far as permissible with a showing of an apparatus suificient for aclear understanding of my process.

Referring to the drawing, 2 2 representfeedpassages, though which thematerial to be operated upon is introducedinto the body of the furnace3. In connection with one of the passages 2 is a conventionalrepresentation of an automatic and continuous feeding device, a worm orscrew feed being represented at 4.

5 represents one of the electrodes, of which any suitable number may beemployed and which may be mounted in any desired manner.

The fused slag passes off through the dis charge-conduit 6, and thevapors or gases generated within the furnace -chamber are dischargedthrough an opening 7 into a trunk or conduit 8, which is connected witha condensin g apparatus, the latter not being shown.

9 9 are openings into the trunk or conduit 8, through which steam may beintroduced into the latter, the steam being supplied from a pipe 10. Itis in this trunk, chamber, or

conduit 8 that the main portion of the hydration of the oxid-vapors fromthe furnace takes place, the steam or water vapor supplied through theapertures 9 supplying the elements for such hydration.

11 11 indicate steam-pipes connected with openings or passages 12,leading into the body of the furnace. Through these vapor of water maybe discharged directly into the furnace-chamber when conditions requirethat this should be done.

The material to be treated is introduced into the furnace and broughtinto contact with the electric current and is rapidly converted intoamolten mass. The exactamount of flux which is used cannot be statedarbitrarily, owing to the variations in the character and richness ofthe materials which may be used and must be in each case relativelydetermined, as it maybe by any person skilled in the art of smeltingores. Likewise the volume and quality of the electric current employedas hereinbefore set forth, for the purposes of heat and electrolysiswill be determined by the work being done and the character of thematerials being treated.

For the complete and certain oxidation and hydration of thesulfur-gases, as before set forth, it is usually desirable to project ajet of steam directly into the furnace, and its quantity must also bedetermined by the quality of the native materials being operated uponand their quantity. However, the material used in carrying out myprocess is such and its physical condition, being broken into smallpieces, is such that large volumes of air are necessarily delivered intothe furnacechamber along with the material. The materials used alsocarry with them a considerable and often very large amount of water, sothat it is not always necessary to introduce the steam into the furnace.Whether or not this is necessary has to be determined by the conditionof the material being operated upon.

A great economy in manufacture is effected by the employment of gypsumin the carrying out of my process from the factthat the resulting acidis chemically pure, so far as arsenic and nitrogen oxids are concerned,these being the impurities most commonly met with in sulfuric acid asnow ordinarily made and requiring expensive purifying processes in orderto free the acid from their presence. I

therefore prefer to use gypsum, as it is not rying out the process, asany one or all of the means may be varied without departing from thespirit of my invention.

Having thus described my invention,'what I claim is- 1. In the art ofmanufacturingsnlfuric acid, the herein-described process, which consistsin subjecting a material containing sulfur to heat and electrolysisproduced by an electric current within a furnace, and applied directlyto the material while in a molten condition, in the presence of anexcess of free oxygen, thereby forming sulfur oxids, and subsequentlyhydrating these, substantially as set forth.

2. In the art of manufacturing sulfuric acid, the herein-describedprocess which consists in subjecting calcium sulfate or gypsum to heatand electrolysis both produced by an elec-' tric current within afurnace, and applied directly to the material while in a moltencondition, and in the presence of an excess of oxygen ,thereby formingsulfur 0Xids,and subsequently hydrating these oxids,substantially as setforth.

3. In the art of manufacturing sulfuric acid free from arsenic, nitrogenoxids, and other common impnrities,the herein-described process whichconsists in subjecting calcium sulfate or gypsum and a flux to heat andelectrolysis, both produced by an electric current within a furnace-chamber containing the materials, and applied directly to andthrough them while in a molten condition in the presence of an excess ofoxygen, thereby forming sulfur oxids, and subsequently hydrating theseoxids, substantially as set forth.

In testimony that I claim the invention above set forth I affix mysignature in presence of two witnesses.

FRANK P. VAN DENBERGH.

Witnesses:

CLINTON B. GIBBS, LYNDON D. Wool).

